Adobe and Yahoo on Wednesday they will offer a service to let publishers run advertisements in Adobe's popular document-reading format.

The new service, Ads for Adobe PDF Powered by Yahoo, presents publishers with an alternative to conventional subscriptions, which, if widely adopted, could open up a new model based on free, ad-supported publishing.

The deal is the latest move by Yahoo to expand the reach of its advertising beyond Yahoo-owned sites. Since last year, Yahoo has signed partnership deals to supply online ads to Web auctioneer eBay, cable TV group Comcastand a consortium of U.S. newspaper groups.

The Adobe service allows publishers to generate revenue by including text-based ads linked to the content of an Adobe PDF (portable document format) page in a separate side panel.

The service is set to begin public testing, which will run several months, the companies said.

The free service requires no special software and is open to U.S. publishers of English-language content, initially.